Bacterial endophytes suppress collar rot of chickpea caused by Sclerotium rolfsii through antagonism and defense enzyme induction

Introduction Collar rot of chickpea, caused by the soil-borne pathogen Sclerotium rolfsii , is commonly managed with chemical fungicides, which may pose environmental and health risks. Bacterial endophytes offer a sustainable alternative through pathogen antagonism and induction of host defense responses. Methods Seventy-three bacterial endophytes isolated from diverse plant sources were screened against S. rolfsii under laboratory conditions. Promising isolates were further evaluated in pot culture through seed priming and soil drenching. Their biocontrol efficacy, plant growth promotion, defense enzyme activities, and biochemical and molecular characteristics were assessed. Results Three isolates, RLB E-30, RLB E-25 and RLB E-64, showed strong antagonistic activity. RLB E-30 recorded the highest mycelial inhibition (82.60%). Seed priming and soil drenching with RLB E-30 resulted in 92.58% seed germination and reduced total disease mortality to 19.43% compared with the untreated control. The isolates were identified as Alcaligenes faecalis RLB E-30, Bacillus velezensis RLB E-25 and Acinetobacter schindleri RLB E-64. Endophyte application enhanced defense-related and antioxidant enzyme activities and promoted plant growth and root development. Conclusion Alcaligenes faecalis RLB E-30 showed the greatest potential for managing chickpea collar rot through direct antagonism and induction of host defense responses. Its combined biocontrol and plant growth-promoting effects highlight its potential as an environmentally sustainable alternative to chemical disease management.